1. Field of the Invention
The present invention relates to a water treatment apparatus using a plasma reactor, and in particular to an improved water treatment apparatus using a plasma reactor which are capable of efficiently removing non-biodegradable pollutants contained in polluted water using a plasma formed by applying a high voltage of 30KV.about.150KV to a plasma reactor. The present invention also relates to water treatment methods.
2. Description of the Conventional Art
Recently, much attention has been paid to preventing fresh air and clean water from being polluted.
Environmental pollution prevention techniques are generally classified into an air pollution prevention technical field, a water pollution prevention technical field, an industrial waste disposal technical field, and a pollution-free technical field. Among the above-described technical fields, the water pollution prevention technical field will be explained.
In the water pollution prevention technical field, much study has been performed in order to provide a waste water treatment system.
However, no efficient and economical technique has been disclosed for supplying clean water. Namely, so far in the industry for treating polluted water, an organic material (such as a carbon hydrogen) contained in the polluted water is simply treated to be removed from the polluted water so that the BOD (Biochemical Oxygen Demand) is lowered thereby, completing a water treatment process. Then the water having lowered BOD is flown to river, lake or the like.
Namely, with industrial advancement and as people are rushed into cities, a various kinds of polluted materials which were not generated in the past are increasingly generated. So far, the thusly generated polluted materials have been treated without accurately analyzing any toxic components contained in the polluted materials and any effects thereof to the environment.
For example, chlorine which is generally used for disinfecting bacteria contained in water is known to form THM (Tri-Hallo-Methane) which may cause cancer.
In addition, polluted water containing much nitrogen and phosphorus is increasingly generated from homes and transferred into rivers, lakes, or the like, for thereby increasing BOD therein.
As shown in FIG. 1, in the conventional water treatment method, polluted water passes through a first stabilization tank and then flows to a concentrator.
The polluted water transferred from the concentrator is separated into a solid sludge and polluted water.
The solid sludge contained in the polluted water is transferred to a post incinerating apparatus through a drying apparatus and an incinerator.
The polluted water is transferred into an air stripper and passes through a second stabilization. The sludge gathered on the bottom of the second stabilization tank is transferred to the sludge gathering apparatus.
The sludge gathered by the sludge gathering apparatus is transferred to the drying apparatus.
In addition, the polluted water passed through the second stabilization tank is transferred to an aeration tank for separating the polluted water into a sludge and a polluted water, and then the polluted water is transferred to an RTO (Regenerative Thermal Oxidizer).
At this time, a part of the sludge transferred into the active sludge reactor is transferred into the sludge gathering apparatus, and another part of the same is transferred into a regenerative thermal oxidizer together with the polluted water passed through the aeration tank, and another part of the same is released to the outside as waste water.
However, the above-described polluted water treatment apparatus is unable to effectively remove nitrogen, phosphorus, or toxic materials contained in the polluted water.
In particular, the polluted materials generated from factories and containing a choline component, namely, PCE (perchloroethylene), PCB (polychlorinated biphenyl), and DCP (dichlorophenol) may contain a very toxic material. Furthermore, the above-described polluted material generates a secondary toxic material upon reaction with a choline component contained therein. Therefore, when the polluted water containing the above-described polluted material is released into a river or lake, the river or lake is seriously damaged compared to other polluted water which does not contain the above-described polluted materials.
In addition, the chlorine-contained polluted material is not easily dissolved under the natural environment nor naturally dissolved into water. There is not a proper method for economically eliminating the above-described pollutants.
For example, in the case of the dyeing component polluted water, dyeing component polluted water contains choline components as well as nitric acid components, so that it is very harmful and has a very high toxicity. The above-described pollutants are controlled as one of the most toxic materials in most countries.
For reference, dyeina factories represent about 6% of the factories which generate pollutants and about 3.5% of the total amount of pollutants. At a glance, such figures seem to cause less pollution problems compared to other pollutants but the pollution degree (treatment-before BOD) is about 24% of the total degree. Therefore, the dyeing component polluted water causes a large pollution problem.
For effectively treating the above-described polluted water, there are known a physical and chemical treating method, a biochemical treating method, a coagulation and sediment method, the Fenton oxidizing method, an electron beam processing method, an activated charcoal adsorption method, a film separation method, and a plasma processing method.
Among the above-described methods, the physical and chemical processing method is directed to preprocessing the pollutant before polluted water is treated. Therefore, the physical and chemical processing method is incapable of actually eliminating pollutants.
In addition, as the biochemical processing method, an activated sludge process is widely used in industry for adsorbing and dissolving organic materials using activated aerobic bacteria. In this method, a lot of sludge is generated, and in particular the dyeing material contained in the dyeing component polluted water is not degraded. Even when it is degraded, it may generate a secondary toxic material, so that the pollutant treating efficiency is very low. In order to overcome the above-described problems, a method which uses an anaerobic bacteria among the biochemical processing method is disclosed. However, this method has a problem in that it takes a long time (tens of days) for processing the non-biodegradable pollutants.
The coagulation and sediment method is capable of eliminating a wide range of pollutants but is incapable of eliminating a dissolvable material such as a soluble component.
The Fenton oxidizing method (disclosed by Fenton of England at the end in the 19th century) is the method for processing polluted water using a phenomenon that strong oxidization occurs when H.sub.2 O.sub.2 and Fe ions react. This method has a disadvantage in that the agent provided for strong oxidization is very expensive.
The ozone processing method is implemented using ozone having a strong oxidizing force. This method is good for dissolving a non-soluble material, deodorizing a predetermined smell, and eliminating coloring components. However, the ozone generator is expensive, and the ozone occurrence efficiency is no more than 5%, so that power consumption is increased.
The electron beam method has an advantage in that it is possible to overcome the problems encountered in the above-described methods. However, a system for generating electron beams and implementing acceleration for the beams is complicated and expensive, so that the operation cost of the system is increased like the ozone processing method. In addition, the depth of water into which electron beams pass through is a few mm, the polluted water should be rapidly flowed over a region which is wide and shallow for thereby implementing a water treatment process. In addition, the electron beam generator is bulky and is designed to generate a high capacity, thereby increasing fabrication cost. Furthermore, the electron beam generator may generate harmful X-rays.
The activated charcoal adsorption method is directed to adsorbing pollutants using an activated charcoal having a plurality of fine holes. In this case, the activated charcoal is recyclable. However, the processing efficiency of the pollutants is decreased, so that it is not used solely.
The film separation method has an advantage in that a film material is separable based on its particle size and chemical affinity by a physical and chemical function of the film material. However, the fabrication cost is increased, and the preprocessing procedure is complicated. In particular, if the preprocessing procedure is not properly performed, the expensive facility may be damaged.
In the method for generating an activated radical based on a plasma for thereby implementing a water treatment, there are the following problems: First, a relatively high electric field (over 2.times.10.sup.5.about.3.times.10.sup.5 Volt/cm) is needed for obtaining electrical insulation destruction under water. Second, since a streamer is quickly transferred by a discharging operation under water, the streamer corona is not continuously implemented, so that an arc or spark easily occurs. Third, even though the streamer corona occurs continuously, since the reactive region of the activated radical generated by the streamer is narrow, it is impossible to effectively eliminate the pollutants. The above-described problem may be overcome by the electron beam method which uses MeV (Mega electron Volts). However, the electron beam method is implemented by a relatively bulky system, and the human body may be hurt.